Grafting on opuntia - what am i doing "wrong"

[ElieEstephane]

Hello everyone!
Late fall i wanted to try my hand at grafting as it could be very useful later on so i thought i'd experiment. The stock i have readily available for free with very large numbers was Opuntia ficus indica. All grafts were done on unrooted pads in my "box bed" under grow lights and ~35 degrees in the same mix and the same pot size. All pads are extensively rooted now. Unfortunately i knocked off most of the grafts. Here's what remained.

My first attempt: Lobivia arachnacantha. Growth exploded in 1 week and it was very fast. Arrow points to where growth started. Current size is after 2 months grafted.

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Second graft: chamaecereus grafted on pad double the size of the first one. In the same period of growth under the same conditions, only this very tiny pup emerged

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Third graft: schlumbergera hybrid. Pretty much did nothing for quite a while. Then the past couple of weeks, only these 2 new tiny stems occured.

20180305_222327-1200x1600.jpg (92.4 KiB) Viewed 2717 times

So why the extreme difference in growth rate even though the pads are much larger

PS: the new pads popping out are very recent so they could not have disturbed growth of the scion.

Thanks for your opinions!

[Hanazono]

I think 2nd one is the failure of grafting.
The scion is not jointed or the Jointed area is not large enough to grow the scion.

[ElieEstephane]

I think 2nd one is the failure of grafting.
The scion is not jointed or the Jointed area is not large enough to grow the scion.

Thanks! Yes it could be the grafting area is too small these are only just experiments so i'll try to match the vascular bundles better.

[snarfie]

chamacereus graft indeed looks like it hasn't connected properly. The schlumbergera will likely keep growing fast but not super fast like other cacti when grafted. Depends on both the schlumbergera cultivar you graft and the stock you use. When grafted on larger hylocereus, almost any Schlumbergera cultivar can be forced to grow, even from the side areoles, but with most other stocks, it will only grow from the areoles at the top of the segment. Growth of a new row of segments should be visible when the segments below are starting to mature.